Floatable units, such as liferafts or platforms are often used in the evacuation of the passengers or crew members from a vessel.
Heeling movements as well as the movements which are caused by the loads such as wind, current or waves, exerted on the vessel render that the position as well as the movements of the vessel are changing all the time. Furthermore, due to the fact that the floatable unit is smaller in size than the vessel the floatable unit moves more rapidly than the vessel.
These movements of the vessel, as well as of the floatable unit are causing the difficulties of entering the floatable unit from the vessel, as the distance, both in height, in the transverse as well as in the longitudinal, direction between the vessel and the floatable unit is varying constantly, whereby it is almost impossible to hold the floatable unit in a secure and fixed position in relation to the vessel.
Often the evacuation of the persons from the vessel takes place during heavy weather, which furthermore influences as well as exerts great forces and loads on the vessel and the floatable unit.
Furthermore, the deck of the vessel, where the evacuation of the persons takes place from are normally placed above the waterline, and thereby above the floatable unit, and may have many different distances depending on the size of the vessel.
The evacuation from the vessel into the floatable unit may be carried out by means of many different arrangements, typically a slide or a chute. More and more often the so called chute is used. The reason for this is that the chute as a vertical escape route is arranged to absorb the vertical variation of the distance between the evacuation point on the vessel and the floatable unit.
If there is a large vertical distance between the deck of the vessel and the floatable unit, and if this distance vary frequently during the evacuation, the chute, in it self is able to absorb this varying distance, due to its length and its thereby build-in flexibility.
However, in the cases where the distance between the deck of the vessel and the floatable unit is limited, a shorter chute might be used. In this case, the longitudinal displacement of the raft in relation to the vessel, will cause the chute to be inclined to such an extent that the chute becomes occasionally unusable.
The above-mentioned drawbacks and disadvantages are primarily explained in connection with the vertical distance. However, similar drawbacks and disadvantages occur in relation to the transverse and longitudinal distances between the evacuation point of the vessel and the floatable unit.
Some known mooring systems consist of two lines which extends from a winch placed on the deck of the vessel and down to separate guiding points, placed on the vessel side above the waterline and towards the liferaft. The turning points are placed in a mutual distance larger than the length of the inflatable raft. The lines are fixed at each corner of the liferaft by means of a glued or welded attachment arrangement.
The known mooring systems have the disadvantage that when the liferafts shall be pulled into the vessel side to evacuate passengers down in the raft great pulling forces have to be used, which affect the area where the lines are fixed. Whereby the raft is easily destroyed in the area around the fixed point for the mooring lines.
The pulling forces in the fixed point for the line are increased further when the vessel and the raft are placed differently in relation to wave trough and wave crest.